Comparative Efficacy of Neonicotinoids and Selected Insecticides in Suppressing Tunneling Activity of Mole Crickets (Orthoptera: Gryllotalpidae) in Turfgrass 1 Juang-Horng Chong 2 J. Agric. Urban Entomol. 26(3): 135 146 (July 2009) ABSTRACT Long-term efficacy of neonicotinoids (clothianidin, imidacloprid, and thiamethoxam), acephate, bifenthrin, and fipronil in suppressing the tunneling activity of mole crickets (Orthoptera: Gryllotalpidae) was investigated in athletic fields in Florence, SC from June to December 2008 and 2009. The proportions of tawny mole cricket (Scapteriscus vicinus Scudder) and southern mole cricket (Scapteriscus borellii Giglio-Tos) were 87% and 13% in 2008 and 78% and 22% in 2009, respectively. Plots treated with insecticides had lower ratings of tunneling damage than the untreated plots, which had the most severe damage in October of 2008 and 2009. Fipronil was the most effective insecticide, which reduced tunneling activity from 4.0 6 0.9 to 0.8 6 0.3 and 5.3 6 0.3 to 1.1 6 0.1 within two weeks after treatment (WAT) in 2008 and 2009, respectively, and maintained effective residual control until December. Neonicotinoids (all active ingredients and formulations), acephate, and bifenthrin did not perform as well as fipronil, but contributed to lowering the damage in the treated plots. The long-term efficacy was not significantly different among products containing clothianidin, imidacloprid, and thiamethoxam. The combination of clothianidin and bifenthrin (Aloft TM ) and imidacloprid and bifenthrin (AllectusH) improved the suppression of tunneling activity only in the first two WAT when compared to products containing only clothianidin (Arena TM ) or imidacloprid (MeritH). The efficacy of Aloft and Allectus against mole crickets was not different between broadcast and granular formulations on most sampling dates. This study demonstrated that products containing fipronil provided turf managers with long-term suppression of mole cricket tunneling damage, while products containing acephate, bifenthrin, and neonicotinoids would only provide suppression for 20 weeks. KEY WORDS acephate, bifenthrin, clothianidin, fipronil, Gryllotalpidae, imidacloprid, Orthoptera, Scapteriscus, thiamethoxam Mole crickets (Orthoptera: Gryllotalpidae) are major pests of turf and pasture grass in the southeastern United States. The major pest mole cricket species of South Carolina are the tawny mole cricket, Scapteriscus vicinus Scudder, and the southern mole cricket, Scapteriscus borellii Giglio-Tos. They cause damage to turfgrass by surface and underground tunneling activities, which leads to mechanical damage, up-rooting, and desiccation of turfgrass. The tawny mole 1 Accepted for publication 29 November 2010. 2 Clemson University, Department of Entomology, Soil, and Plant Sciences, Pee Dee Research & Education Center, 2200 Pocket Road, Florence, South Carolina 29506. E-mail: juanghc@clemson.edu 135
136 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009) cricket causes additional damage by feeding on the turfgrass, while the southern mole cricket mainly feeds on other small insects (Hudson 1995). The severity of mole cricket tunneling damage differs among warm-season turfgrass species. Grasses with a dense canopy and coarse root system, such as St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], are not damaged as severely as grasses that have an open growth habit (e.g., bahiagrass, Paspalum notatum Fluegge), shallower root system (e.g., closely mowed fairways of bermudagrass, Cynodon spp.), or finer texture (some cultivars of St. Augustinegrass and bermudagrass) (Potter 1998, Braman et al. 2000). Management of mole crickets on athletic fields, golf courses, and residential and commercial landscapes rely heavily on insecticidal treatments. The most common insecticides used for managing mole cricket population and tunneling activity are organophosphates (e.g., acephate), pyrethroids (e.g., bifenthrin and deltamethrin), and phenylpyrazoles (e.g., fipronil). Neonicotinoids are also used for managing mole crickets. Insecticides are often applied between the adult flight and egg hatch (Hudson 1995). The periods when mole crickets are active in flight and laying eggs vary from year to year. In addition, adult flights during periods of dry weather do not always result in reproduction. Therefore, it is prudent to monitor the number and size of immature mole crickets with soil flushes of soapy solution and to adjust application timing to target the vulnerable immature mole crickets. Treatments in late spring or early summer targeting adult mole crickets are largely ineffective. However, the early-summer treatments to golf courses may help to suppress the tunneling activities of adult mole crickets, provide residual control of immature mole crickets, and maintain a playable surface. Neonicotinoids are acetylcholine mimics and were first developed in the 1970s (Jeschke & Nauen 2008). With the development and introduction of imidacloprid in 1980s 1990s, neonicotinoids have become one of the most intensively used families of insecticides worldwide (Jeschke & Nauen 2008). Individual neonicotinoid products demonstrated varying levels of control for mole cricket population and activity in field and greenhouse studies, which appeared to be related to application timing, formulation, and irrigation practices. Thiamethoxam was ineffective against adults and nymphs older than the third instar (Brandenburg et al. 2005). More irrigation appeared to help the movement of imidacloprid into the soil and achieved higher control of mole cricket activity (Xia & Brandenburg 2000). Although the performance of individual neonicotinoid products for mole cricket management had been investigated in field trials (Hertl & Brandenburg 1998, Harris 1999, Hertl et al. 2001), there has been no side-by-side comparison of multiple neonicotinoid products in turfgrass systems. The objectives of this study included a comparison of the long-term efficacy of selected neonicotinoids and other frequently used turfgrass insecticides in suppressing the tunneling activity of mole crickets when applied in early summer. A second objective was to compare the efficacy of broadcast and granular formulations of some neonicotinoid products against the mole crickets. By understanding the difference among active ingredients and formulations, particularly among neonicotinoids, in suppressing tunneling activity, this study will help to improve the management of mole crickets in turfgrass systems.
CHONG: Suppression of mole crickets with neonicotinoids 137 Materials and Methods This study was conducted on athletic fields of Francis Marion University, Florence, SC from June to December in 2008 and 2009. The athletic fields were chosen for the study because they harbored a large population of mole crickets that annually caused significant damage. The soil type is Norfolk loamy sand. The fields were established with hybrid bermudagrass (Cynodon dactylon [L.] Pers. x C. transvaalensis Burtt-Davy, cv. Tifway ) and overseeded with ryegrass (Lolium perenne L.) in the winter. The turfgrass was mowed to a height of 1.7 cm and irrigated three times a week with an estimated application volume of 5 cm per 6.5 cm 2 in the summer. The amount of thatch was negligible. The athletic fields were divided into 10 3 10 m plots arranged in randomized complete block design. All treatment had four replicates. The fields used for the 2008 and 2009 experiments were located adjacent to each other. Mole crickets were collected from the test plots using a detergent-solution flush method (Hudson 1995) prior to the insecticide applications. The detergent solution was prepared by thoroughly mixing 30 ml of lemon-scented liquid dish detergent in 7.2 L water. Mole crickets that surfaced after pouring the detergent solution on the ground were collected and brought back to the laboratory for identification. Ten insecticides were applied to the plots to evaluate their residual effects on the tunneling activity over a six-month period (Table 1). The tested active ingredients (AI) included acephate, bifenthrin, clothianidin, fipronil, imidacloprid, and thiamethoxam. Clothianidin, imidacloprid, and thiamethoxam are neonicotinoids registered for management of various arthropod pests in turfgrass. Acephate, bifenthrin, and fipronil are frequently used for control of mole crickets by turfgrass managers and were therefore chosen for comparison. Broadcast spray and granular formulation of Aloft TM and AllectusH, which are combinations of clothianidin and bifenthrin and imidacloprid and bifenthrin, respectively, were also applied for comparison. All treatments were applied on 2 June 2008 and 8 June 2009. The soil was moist from irrigation the day before. The broadcast sprays were applied with a customized compressed-co 2 sprayer (at 2.8 kg-force/cm 2 ), mounted on a modified golf cart and fitted with V8002 nozzles, at an application volume of 410 L/ha. Granules were measured in the laboratory and applied to the plots with a calibrated ScottsH Handy GreenH handheld spreader (Scotts Company, Marysville, OH). Applications were made in the late morning of 2 June 2008 when the ambient temperature was 30uC, the soil temperature (at 10 cm depth) was 28uC, the relative humidity was 36%, and the wind speed was 4 km/hr. On 8 June 2009, the ambient temperature in the late morning was 28uC, the soil temperature at 10-cm depth was 27uC, relative humidity was 42%, and the wind speed was 5 km/hr. All plots were irrigated (5 cm per 6.5 cm 2 ) within 4 h of treatment to release the active ingredients from the granules into the soil. The surrounding field not used for this study was spot-treated twice with bifenthrin (Bifenthrin GC G at 0.22 kg AI/ha/application; Southern Agricultural Insecticides, Inc., Hendersonville, NC) over the course of this study to maintain a playable surface on these untreated fields. A one meter untreated border was maintained between the test plots and surrounding field.
138 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009) Table 1. Trade names, active ingredient concentrations, application rates and company information of the insecticides tested against the tunneling activity of mole cricket in turfgrass at the athletic field of Francis Marion University, Florence, SC. Trade name Application rate 1 (product per hectare) Application rate (AI per hectare) Company Aloft TM LC SC 1.7 L 453 g clothianidin + 224 g bifenthrin Arysta LifeScience, Cary, NC Aloft TM GC G 180 kg 450 g clothianidin + 225 g Arysta LifeScience bifenthrin Arena TM 50 WDG 0.9 kg 450 g clothianidin Valent USA Corporation, Walnut Creek, CA AllectusH SC 8.4 L 454 g imidacloprid + 363 g bifenthrin Bayer Environmental Science, Research Triangle Park, NC AllectusH G 225 kg 450 g imidacloprid + 360 g bifenthrin Bayer Environmental Science MeritH 2F 1.9 L 455 g imidacloprid Bayer Environmental Science Meridian TM 25 WG 1.2 kg 300 g thiamethoxam Syngenta Professional Products, Greensboro, NC OrtheneH TT&O 97 4.37 kg 4,239 g acephate Valent USA Corporation TalstarH One 3.2 L 254 g bifenthrin FMC Corporation, Philadelphia, PA TopChoice TM 97.5 kg 13.9 g fipronil Bayer Environmental Science 1 All insecticides were applied at or near the maximum rate allowed per hectare per year. Before and after treatments, this study was evaluated biweekly for fresh tunneling activity from June to December using the method of Cobb & Mack (1989). A 1-m 2 grid built with a PVC pipe frame and divided into nine subsections was placed randomly in each plot. The grid was never put within 0.5 m of the edge of individual plots to avoid collecting data from areas of potential drift or spill-over of insecticides from the next plot. Based on the number of tunnels in the grid, a rating of 0 (no tunnel in any subsection) to 9 (at least one tunnel in every subsection) was given to each plot. Three and four ratings were taken from each plot on each sampling date in 2008 and 2009, respectively, and the mean ratings from each plot were used p for ffiffiffiffiffiffiffiffiffiffiffiffiffiffi statistical analyses. Data from each sampling date were transformed with xz0:5 to normalize data distribution before analysis of variance (ANOVA) (PROC GLM, SAS Institute 1999). When significant differences among the treatments were detected at a 5 0.05, Fisher s least significant difference (LSD) test was used to separate the means.
CHONG: Suppression of mole crickets with neonicotinoids 139 Results and Discussion The athletic fields were severely infested with mole crickets. The damage ratings averaged 3.9 (range 1.3 7) in 2008 and 4.5 (range 2.5 8.25) in 2009, and they were not different among the plots prior to the treatment in early June (Tables 2 and 3). A total of 23 and 42 adult and late-instar mole crickets were collected before the treatment in 2008 and 2009, respectively. The mole cricket population was composed of 87% tawny mole crickets and 13% southern mole crickets in 2008, and 77% tawny mole crickets and 22% southern mole crickets in 2009. The mole crickets caused significant damage to turfgrass in the untreated plots over the course of the study, with the highest ratings observed in October in both years. Untreated plots had consistently higher damage ratings than plots treated with any insecticides (Tables 2 & 3). Fipronil (ChipcoH Choice TM and TopChoice TM ), which is the preferred active ingredient for red imported fire ant (Solenopsis invicta Buren; Hymenoptera: Formicidae) and mole cricket management in commercial and recreational turfgrasses, was the most effective insecticide in suppressing the tunneling activity of mole crickets in this study. The damage rating in plots treated with fipronil was reduced rapidly from an average of 4.0 in the pre-treatment evaluation to 0.8 in 2008 (Table 2), and from 5.3 to 1.1 in 2009 (Table 3), within two weeks after treatment (WAT). Fipronil significantly reduced mole cricket activity when compared to the untreated plots. Acephate (OrtheneH TT&O 97) and bifenthrin (TalstarOneH) also reduced the tunneling activity within 2 WAT compared to the untreated control in both years (Tables 2 & 3). The damage ratings in the acephate- and bifenthrin-treated plots were not reduced as rapidly as in plots treated with fipronil. In addition, acephate and bifenthrin appeared to lose residual control more quickly than fipronil with the damage ratings as high as the untreated plots by 21 and 20 WAT in 2008 and 2009, respectively. Similarly, Unruh & Buss (2003) reported a faster reduction of tunneling activity by fipronil compared to bifenthrin within 10 d after treatment (DAT) at a golf course in northern Florida. In the same study, the tunneling activity in bifenthrin-treated plots was greater than those treated with fipronil by 56 DAT but less than the untreated plots up to 77 DAT. Fipronil has extremely long residual in the soil. The half-life of soil photolysis of fipronil is about 34 d; however, the half-lives for aerobic and anaerobic metabolism in soil are 630 693 and 123 d, respectively (CDPR 2001). Half-lives of bifenthrin in anaerobic and aerobic soil are 97 156 and 65 125 d (EPA 1988). Half-life of acephate in aerobic and anaerobic soil is 3 6 d (EPA 1987), considerably shorter than fipronil and bifenthrin. Residual toxicity and repellency of fipronil and its metabolites were effective against late-instar mole crickets up to 120 d (Cummings et al. 2006). The long residual activity of fipronil makes the insecticide attractive to turfgrass managers. The chemical and biological attributes that made neonicotinoids one of the most widely used insecticides in the world s crop production, human and animal health, structural, and recreational pest management include their broadspectrum of activity, unique mode of action, systemic action in living plant tissues, and extended residual activity (Elbert et al. 2008, Jeschke & Nauen 2008). In the turfgrass production and management industry, neonicotinoid products are frequently used for preventive and early curative control of white
140 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009) Table 2. Mean ratings (±SEM) of tunneling activity (0 = no tunnel; 9 = all nine subsections had at least one tunnel) in turfgrass plots (100 m 2 ) treated with selected insecticides in 2008. Insecticide 2 June (0 WAT 1 ) 16 June (2 WAT) 30 June (4 WAT) 16 July (6 WAT) Untreated 3.6 6 0.6 4.5 6 0.9 ab 4.3 6 0.8 a 3.2 6 1.0 a Aloft LC SC 4.1 6 1.0 2.5 6 0.6 d 2.0 6 0.3 cd 1.0 6 0.5 b Aloft GC G 4.3 6 0.8 3.3 6 0.7 abc 3.1 6 0.4 b 1.3 6 0.7 b Arena 50 WDG 4.4 6 0.2 5.2 6 0.3 a 2.3 6 0.2 bc 1.3 6 0.4 b Allectus SC 4.2 6 1.1 3.2 6 0.7 bcd 1.8 6 0.2 cd 0.3 6 0.1 b Allectus G 4.3 6 0.7 2.6 6 0.4 cd 1.3 6 0.4 de 0.3 6 0.2 b Merit 2F 3.8 6 0.8 3.3 6 0.8 bcd 1.8 6 0.2 cd 1.0 6 0.5 b Meridian 25 WG 4.2 6 0.3 4.3 6 0.6 abc 2.1 6 0.1 c 1.2 6 0.4 b Orthene TT&O 97 2.8 6 0.7 2.1 6 0.4 d 1.1 6 0.2 ef 1.3 6 0.8 b TalstarOne 3.2 6 0.5 2.7 6 0.4 bcd 2.0 6 0.2 cd 0.6 6 0.4 b TopChoice 4.0 6 0.9 0.8 6 0.3 e 0.5 6 0.1 f 0.1 6 0.1 b ANOVA statistics 2 F 0.53 4.64 10.66 2.43 P 0.8593 0.0004, 0.0001 0.0267 1 WAT 5 week after treatment. 2 df for all ANOVA 5 10, 33. Means followed by the same letter within a column are not significantly different (LSD test at a 5 0.05). Table 3. Mean ratings (±SEM) of tunneling activity (0 = no tunnel; 9 = all nine subsections had at least one tunnel) in turfgrass plots (100 m 2 ) treated with selected insecticides in 2009. Insecticide 8 June (0 WAT 1 ) 22 June (2 WAT) 7 July (4 WAT) 21 July (6 WAT) Untreated 4.3 6 0.6 4.8 6 0.8 a 4.5 6 0.5 a 4.8 6 0.8 a Aloft LC SC 4.1 6 0.9 2.0 6 0.4 bc 1.9 6 0.3 bc 1.4 6 0.4 bc Aloft GC G 4.5 6 0.6 2.8 6 0.5 b 2.6 6 0.2 b 1.5 6 0.9 bc Arena 50 WDG 4.8 6 0.3 4.1 6 0.2 a 2.4 6 0.2 b 1.4 6 0.4 bc Allectus SC 4.6 6 0.9 2.9 6 0.7 b 1.8 6 0.3 bc 1.1 6 0.2 bc Allectus G 4.3 6 0.6 2.8 6 0.3 b 1.3 6 0.5 cd 1.4 6 0.2 bc Merit 2F 4.0 6 0.8 4.5 6 0.3 a 2.4 6 0.4 b 2.4 6 0.2 b Meridian 4.3 6 0.3 4.8 6 0.5 a 2.6 6 0.2 b 2.3 6 0.5 b Orthene TT&O 97 4.8 6 0.6 2.3 6 0.5 b 1.0 cd 1.4 6 0.2 bc TalstarOne 4.1 6 0.9 2.8 6 0.3 b 1.8 6 0.3 bc 1.3 6 0.5 bc TopChoice 5.3 6 0.3 1.1 6 0.1 c 0.6 6 0.2 d 0.5 6 0.2 c ANOVA statistics 2 F 0.35 9.10 9.25 4.04 P 0.9609, 0.0001, 0.0001 0.0011 1 WAT 5 week after treatment. 2 df for all ANOVA 5 10, 33. Means followed by the same letter within a column are not significantly different (LSD test at a 5 0.05).
CHONG: Suppression of mole crickets with neonicotinoids 141 Table 2. Extended. 30 July (8 WAT) 18 August (11 WAT) 2 September (13 WAT) 18 September (15 WAT) 2 October (17 WAT) 4.9 61.2 a 5.4 6 1.0 a 3.0 6 1.7 3.3 6 0.6 a 7.4 6 0.5 a 2.9 6 0.6 b 3.1 6 0.4 bc 1.2 6 0.6 0.8 6 0.4 cd 2.4 6 0.8 bcd 3.2 6 1.3 b 3.4 6 1.0 b 0.8 6 0.4 1.1 6 0.5 bcd 2.7 6 0.7 bc 1.8 6 0.2 b 2.2 6 0.1 bcd 0.8 6 0.4 1.3 6 0.6 bcd 1.9 6 0.6 bcde 2.5 6 0.1 b 3.1 6 0.1 bc 0.7 6 0.1 0.8 6 0.2 bcd 0.8 6 0.3 e 2.2 6 0.3 b 2.5 6 0.2 bcd 0.2 6 0.1 0.5 6 0.2 d 1.2 6 0.4 cde 3.1 6 0.3 ab 3.3 6 0.5 b 2.2 6 1.7 2.8 6 0.7 a 3.0 6 0.7 b 2.6 6 0.2 b 2.7 60.2 bcd 1.5 6 0.7 2.1 6 0.3 ab 2.6 6 0.6 bcd 1.8 6 0.3 b 1.8 6 0.2 cde 0.4 6 0.4 0.8 6 0.3 bcd 1.1 6 0.3 de 2.0 b 1.5 6 0.6 de 1.2 6 1.0 1.9 6 0.8 abc 1.9 6 0.7 bcde 0.2 6 0.1 c 1.0 6 0.6 e 0.1 6 0.1 0.3 6 0.2 d 0.7 6 0.4 e 6.48 4.82 1.10 3.80 7.94, 0.0001 0.0003 0.3901 0.0018, 0.0001 Table 3. Extended. 3 August (8 WAT) 17 August (10 WAT) 31 August (12 WAT) 16 September (14 WAT) 29 September (16 WAT) 5.1 61.0 a 5.3 6 0.9 a 6.1 6 1.0 a 6.0 6 1.1 a 6.8 6 0.5 a 1.9 6 0.3 bc 1.9 6 0.1 bc 1.8 6 0.7 bc 2.1 6 0.3 b 3.0 6 0.5 b 1.6 6 0.6 c 1.9 6 0.5 bc 1.6 6 0.2 bc 2.0 6 0.4 b 2.8 6 0.5 b 2.1 6 0.3 bc 2.3 6 0.1 bc 1.6 6 0.3 bc 2.3 6 0.6 b 2.0 6 0.5 bcd 1.9 6 0.3 bc 2.0 6 0.2 bc 1.9 6 0.4 bc 1.8 6 0.6 b 1.9 6 0.4 bcd 1.8 6 0.3 c 1.8 6 0.3 c 1.4 6 0.7 bc 1.5 6 0.2 b 1.3 6 0.3 cd 2.5 6 0.4 b 2.9 6 0.5 b 2.3 6 0.8 b 2.3 6 0.1 b 2.3 6 0.5 bcd 2.4 6 0.2 bc 2.6 6 0.2 bc 2.1 6 0.7 b 2.1 6 0.3 b 2.5 6 0.6 bc 1.5 6 0.3 c 1.6 6 0.2 c 1.6 6 0.2 bc 1.8 6 0.3 b 2.2 6 0.8 bcd 2.1 6 0.2 bc 1.9 6 0.3 bc 1.8 6 0.9 bc 1.4 6 0.4 b 2.6 6 0.6 bc 0.3 6 0.1 d 0.4 6 0.1 d 0.5 6 0.2 c 0.4 6 0.2 c 1.0 6 0.2 d 8.31 9.72 3.81 6.63 6.21, 0.0001, 0.0001 0.0017, 0.0001, 0.0001
142 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009) Table 2. Extended. 16 October (19 WAT) 31 October (21 WAT) 11 November (23 WAT) 25 November (25 WAT) 9 December (27 WAT) 8.3 6 0.1 a 8.2 6 0.3 a 8.2 6 0.2 a 6.4 6 1.1 a 4.8 6 0.4 a 4.8 6 0.8 bc 7.9 6 0.5 a 6.2 6 1.0 ab 5.6 6 0.4 ab 4.3 6 0.5 a 4.4 6 0.8 bc 7.1 6 0.7 ab 5.8 6 0.9 ab 3.4 6 0.9 bcde 4.4 6 0.9 a 5.3 6 1.2 b 7.1 6 0.8 ab 6.4 6 0.8 ab 5.4 6 0.6 abc 4.6 6 0.5 a 4.1 6 0.8 bc 6.5 6 0.5 ab 4.4 6 0.8 bc 3.1 6 0.6 cdef 3.2 6 0.6 abc 3.3 6 0.5 bcd 5.5 6 1.0 b 3.5 6 0.8 c 2.3 6 1.2 ef 2.4 6 1.0 bc 3.2 6 0.4 cd 7.7 6 0.4 a 5.3 6 0.9 bc 2.9 6 0.6 def 4.3 6 1.0 ab 4.3 6 0.6 bc 7.5 6 0.2 a 5.9 6 0.4 ab 4.3 6 0.4 abcd 4.4 6 0.5 a 4.8 6 0.5 bc 6.7 6 0.9 ab 5.8 6 0.9 ab 3.2 6 0.8 cdef 3.1 6 0.8 abc 4.0 6 0.2 bcd 6.7 6 0.1 ab 5.9 6 1.0 ab 3.8 6 0.4 abcd 3.5 6 0.7 abc 2.4 6 0.6 d 5.5 6 0.6 b 3.3 6 0.6 c 1.3 6 0.4 f 1.8 6 0.6 c 4.48 2.09 2.96 3.95 2.01 0.0005 0.0550 0.0090 0.0013 0.0639 Table 3. Extended. 13 October (18 WAT) 26 October (20 WAT) 9 November (22 WAT) 23 November (24 WAT) 8 December (26 WAT) 7.5 6 0.6 a 7.8 6 0.3 a 6.5 6 0.8 a 5.5 6 0.9 ab 4.7 6 0.4 a 4.3 6 0.8 b 5.9 6 0.3 ab 5.0 6 0.2 a 5.6 6 0.2 a 4.4 6 0.6 ab 3.6 6 0.6 b 5.0 6 0.7 b 5.3 6 0.8 a 4.4 6 0.4 abc 4.8 6 0.4 a 4.6 6 0.9 b 5.0 6 0.5 b 5.6 6 0.5 a 5.4 6 0.5 ab 4.5 6 0.5 ab 3.8 6 0.9 b 5.9 6 0.9 ab 5.0 6 0.5 a 4.5 6 0.4 abc 4.3 6 0.7 ab 3.3 6 0.5 bc 5.3 6 1.0 b 4.5 6 0.3 ab 4.0 6 0.9 abcd 4.6 6 0.4 ab 3.3 6 0.3 bc 5.8 6 1.1 ab 5.1 6 0.8 a 3.6 6 0.4 bcd 3.5 6 0.6 abc 4.0 6 0.6 b 6.4 6 0.4 a 5.9 6 0.4 a 4.3 6 0.5 abc 4.3 6 0.5 ab 4.5 6 0.5 b 6.5 6 0.8 ab 5.6 6 1.0 a 3.1 6 0.7 cd 3.5 6 0.7 bc 3.9 6 0.2 b 5.9 6 0.6 ab 5.1 6 0.7 a 3.6 6 0.5 bcd 3.3 6 0.7 bc 1.5 6 0.7 c 2.1 6 0.4 c 3.1 6 0.5 b 2.4 6 0.3 d 2.3 6 0.4 c 3.79 5.16 1.65 2.57 2.22 0.0018 0.0002 0.1345 0.0203 0.0416
CHONG: Suppression of mole crickets with neonicotinoids 143 grubs. Previous studies reported that the efficacy of neonicotinoids against mole crickets was lower than that of fipronil but comparable to that of acephate (Harris 1999, Hertl et al. 2001). In this study, the reduction of tunneling activity by neonicotinoids (as a group) was consistently lower than fipronil up to 11 WAT in 2008 (Table 2) and 8 WAT in 2009 (Table 3). Although the tunneling activity ratings in plots treated with neonicotinoids were slightly higher than those treated with acephate and bifenthrin in both years, the difference was more often statistically insignificant. Overall, there was no difference in the efficacy among products containing only neonicotinoids, including ArenaH 50 WDG (clothianidin), MeritH 2F (imidacloprid), and Meridian TM 25 WG (thiamethoxam) (Tables 2 & 3). In 2008, the damage ratings in plots treated with Arena were higher at 2, 19, and 25 WAT and lower at 15 WAT than in plots treated with Merit, while the ratings of Arena- and Meridiantreated plots were often similar (Table 2). In 2009, the damage ratings of Arena-, Meridian-, and Merit-treated plots were similar for most sampling dates, except for 20 WAT when Arena achieved slightly greater suppression of mole cricket tunneling activity than Meridian (Table 3). Clothianidin and thiamethoxam are chemically more similar to each other as members of thianicotinoids than to imidacloprid (chloronicotinoids, which also includes acetamiprid). Thiamethoxam can be converted to clothianidin in insects and plants, suggesting that thiamethoxam may be a proinsecticide (Nauen et al. 2003, Ford & Casida 2008). The lower activity of clothianidin and thiamethoxam against mole cricket may justify the suggestion of suppression on the labels of Arena and Meridian. There is no consensus on the comparative efficacy among various neonicotinoid products (Bi & Toscano 2007, Koppenhofer et al. 2002, Herbert et al. 2008, van Herk et al. 2008, Koppenhofer & Fuzy 2008, Oliver et al. 2009). There may be differences in the efficacy among neonicotinoids depending on the chemical properties of the active ingredients, production and environmental conditions, application timing, and application method or formulation. The results of this study suggested that there is no justification to favor one neonicotinic compound over another for suppressing mole cricket activity. The combination of clothianidin and bifenthrin in Aloft and imidacloprid and bifenthrin in Allectus did not improve the suppression of mole cricket tunneling activity when compared to products containing only clothianidin (Arena) or imidacloprid (Merit) (Tables 2 & 3). Although Allectus (both liquid and granular formulations) resulted in numerically lower tunneling ratings than Aloft in 2008, the difference was not significantly different for most sampling dates. In 2009, the damage ratings of plots treated with Allectus and Aloft were almost identical in most sampling dates. The higher efficacy of Allectus may be the result of a higher concentration of bifenthrin in the product, which had a difference of 135 g AI per hectare from Aloft. TalstarOne had similar bifenthrin content and performed as well as Aloft and Allectus. Xia et al. (2000) showed that the same amount of deltamethrin applied as granules (DeltaGardH 0.1G at 146 g AI/ha) caused significantly higher mortality in mole crickets than broadcast sprays (DeltaGardH 5 SC at 144 g AI/ha) at 7 DAT but not 14 DAT. However, in this study, the efficacy of Aloft and Allectus was not different between broadcast spray and granular formulations, except for Aloft at 2 and 4 WAT, when Aloft SC provided faster reduction in the tunneling activity than Aloft G (Table 2). Similarly, broadcast spray and granular formulation of
144 J. Agric. Urban Entomol. Vol. 26, No. 3 (2009) equal amount of bifenthrin (TalstarH G vs TalstarOne) and imidacloprid + bifenthrin (Allectus G vs Allectus SC) were not different in their efficacies against southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), in St Augustinegrass (Chong, unpublished data). This study showed that fipronil is the most effective product against mole crickets in a turfgrass system because of its quick reduction of tunneling activity and long residual effect. However, with the higher cost of fipronil products and increased scrutiny from the U.S. Environmental Protection Agency into its potentially detrimental environmental impacts on non-target organisms, turfgrass managers may decide to use other alternatives. Other viable alternatives include products containing bifenthrin and acephate. The efficacy of neonicotinoids against mole crickets was not different from bifenthrin and acephate. The various active ingredients and formulations of neonicotinic products were similar in their efficacy in suppressing mole crickets. This study demonstrated that products containing fipronil provided turf managers with six-month suppression of mole cricket tunneling activities. Products containing acephate, bifenthrin, and neonicotinoids were similar in their efficacy against mole cricket activities and provided suppression for up to 20 weeks. Acephate, bifenthrin, and neonicotinoids can serve an important role as potential, albeit less efficacious, alternative to fipronil. As this and other studies had demonstrated, the comparative efficacy of neonicotinoids appeared to differ depending on the insect species, production system, application timing and application method or formulation. A better understanding of the potential differences among the various neonicotinoid products in managing turfgrass pests can only be achieved with detailed comparative studies in the future. Acknowledgment I am grateful to Fred Kunz, the ground maintenance crew, and the Athletic Department of the Francis Marion University for an opportunity to conduct this experiment on site and their assistance in the maintenance of the experimental plots. Fran Wimberly, Jessie Strickland, and Gerard Jebaily of Clemson University assisted in data collection and site maintenance. Arysta LifeScience, Bayer Environmental Science, FMC Corporation, Syngenta Professional Products, and Valent USA Corporation generously provided the products tested in this study. Robert Bellinger and Francis Reay-Jones of Clemson University and one anonymous reviewer provided helpful comments to an earlier draft of this manuscript. This material is based upon studies supported by NIFA/USDA under project number SC-1700351. This manuscript is Technical Contribution no. 5771 of the Clemson University Experiment Station. References Cited Bi, J. L. & N. C. Toscano. 2007. Current status of the greenhouse whitefly, Trialeurodes vaporariorum, susceptibility to neonicotinoid and conventional insecticides on strawberries in southern California. Pest Manag. Sci. 63: 747 752. Braman, S. K., R. R. Duncan, W. W. Hanna & W. G. Hudson. 2000. Evaluation of turfgrasses for resistance to mole crickets (Orthoptera: Gryllotalpidae). HortScience 35: 665 668. Brandenburg, R. L., Y. Xia & B. Watson. 2005. Comparative toxicity and efficacy of selected insecticides in field and greenhouse assays against tawny and southern mole crickets (Orthoptera: Gryllotalpidae). J. Entomol. Sci. 40: 115 125.
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